In 1988, San Francisco police officer Donnie Cartwright went into a burning building and braved flying glass and smoldering debris to try to rescue an infant trapped by the flames.

Yesterday, the officer, who received a commendation for the heroic attempt to save that child's life, was formally charged with molesting a 13-year-old boy who had been left in Cartwright's care at Mission Police Station.

Cartwright, 39 and a member of the police force for nine years, pleaded not guilty to a felony count of committing a lewd and lascivious act upon a child under 14 years of age.

He said he is "devastated" by the accusation.

"It's demeaning," Cartwright said. "I feel like I've done a good job for the city. You think you're helping people and (then) someone can say whatever they want to say and it turns into this."

But Assistant District Attorney Frank Passaglia said he would not have filed the charge if he did not think there was evidence to support it.

Cartwright turned himself in to authorities Wednesday after a warrant for his arrest was issued. He later was released on $5,000 bail and was suspended without pay from the department, which is conducting an administrative investigation of the allegation.

The charge stems from an April 12 incident in which Cartwright was asked to monitor a boy who was brought to Mission Police Station with his parents, who were arrested on suspicion of shoplifting.

After being turned over to Child Protective Services later the same day, the boy told a counselor that Cartwright had fondled him while Cartwright and the child were alone in a conference room at the station, Passaglia said. The boy said Cartwright strip-searched him and asked him to masturbate, the prosecutor said.

Cartwright's attorney, Joe O'Sullivan, accused the prosecution of relying on the story of a child with a reputation for being "untrustworthy and manipulative." O'Sullivan said the child made up his claims to seek revenge against police for arresting his parents. O'Sullivan added that police searches of Cartwright's home and police locker yielded no evidence to support the case.

Passaglia conceded that much of the case will rely on the boy's testimony but said that he considers the boy a "credible witness, who has nothing to gain by fabricating the allegations."

Cartwright was one of two officers who received a police commission commendation in 1988 for "outstanding bravery" for twice attempting to rescue an infant from a burning building. The baby perished in the fire.

Cartwright was the partner of James Guelff, who was killed in November in a shootout with a heavily armed man at Pine and Franklin streets. Cartwright has since become an outspoken advocate in the department's attempt to arm its officers with automatic weapons.